Hydraulic control device

ABSTRACT

In a hydraulic control device switchable between a first state in which a first oil is supplied from a first pump to a hydraulic operation part via a bypass valve and a second state in which the first oil supplied from the first pump is pressurized by using the second pump and the pressurized first oil is supplied, as a second oil, to the hydraulic operation part, when the second pump is stopped in the second state, control that gradually decreases a target rotation speed of the second pump is performed, and rates at which the target rotation speed of the second pump decreases differ in a case where the second pump is stopped in an operation-allowed region and in a case where the second pump is stopped when the second pump is determined as in an operation-disallowed region.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Japan application serialno. 2019-205046, filed on Nov. 12, 2019. The entirety of theabove-mentioned patent application is hereby incorporated by referenceherein and made a part of this specification.

BACKGROUND Technical Field

The disclosure relates to a hydraulic control device in which a secondpump and a bypass valve are connected in parallel between a first pumpand a hydraulic operation part, and which supplies a first oil from thefirst pump to the hydraulic operation part via the bypass valve, orwhich pressurizes the first oil by using the second pump and suppliesthe pressurized first oil as a second oil to the hydraulic operationpart.

Description of Related Art

For example, Patent Document 1 discloses a hydraulic control device of avehicle transmission in which a second pump (electric pump) and a bypassvalve (check valve) operated by the drive of a motor are connected inparallel between a first pump (mechanical pump) and a hydraulicoperation part of the transmission. In this case, when the engine isstarted, first, a first oil is supplied from the first pump to thehydraulic operation part via the bypass valve (first state). After that,the second pump is driven by the drive of the motor, and the first oilsupplied from the first pump is pressurized by the second pump, and thepressurized first oil is supplied as the second oil from the second pumpto the hydraulic operation part (second state). The hydraulic operationpart includes, for example, an oil chamber of a pulley (drive pulley anddriven pulley) of a belt-type continuously variable transmission.

In the hydraulic control device having the above configuration,switching between the first state in which the first oil is supplied tothe hydraulic operation part (continuously variable transmission) andthe second state in which the second oil is supplied is performed byopening and closing the bypass valve. That is, when the discharge amount(flow rate) of the second oil from the second pump exceeds the flow rate(discharge amount of the first oil from the first pump) of the first oilpassing through the bypass valve, the hydraulic pressure (line pressurePH) in the downstream oil passage of the bypass valve becomes higherthan the hydraulic pressure (output pressure P1) in the upstream oilpassage. In this way, the bypass valve is closed, and the supply of thefirst oil from the first pump to the hydraulic operation part via thebypass valve is switched to the supply of the second oil from the secondpump to the hydraulic operation part. As a result, the flow of the firstoil to the oil passage is blocked, and the second oil is pumped to thehydraulic operation part by the second pump. On the other hand, when thedischarge amount of the second pump is reduced due to the stop or thelow rotation state of the second pump, the bypass valve is open, and thefirst oil is supplied to the hydraulic operation part.

However, in the hydraulic control device with the above configuration,even though the second pump is stopped to switch the second state to thefirst state, at the time of stopping the second pump, if the targetrotation speed is lowered at a large rate, there is a concern that thefuel efficiency deteriorates due to the drastic decrease of thehydraulic pressure of the oil supplied to the hydraulic operation part.Meanwhile, in the case where the second pump is determined as in anoperation-disallowed region from the perspective such as operationcondition, performance, etc., it is necessary quickly stop the secondpump to shorten the operation time in the operation-disallowed region.Therefore, at the time of stopping the second pump, it requires asolution for suitably controlling the rotation speed of the second pumpin response to the operation state of the second pump.

PRIOR ART DOCUMENT Patent Document

-   Patent Document 1: Japanese Laid-open No. 2015-200369

The disclosure provides a hydraulic control device capable of suitablycontrolling a rotation speed at a time of stopping a second pump inresponse to an operation state of the second pump.

SUMMARY

In a hydraulic control device of the disclosure, a bypass valve (58) anda second pump (30) driven by a motor (32) are connected in parallelbetween a first pump (20) and a hydraulic operation part (56) of atransmission. The hydraulic control device is configured to beswitchable between a first state and a second state. In the first state,a first oil is supplied from the first pump (20) to the hydraulicoperation part (56) via the bypass valve (58). In the second state, thefirst oil supplied from the first pump (20) is pressurized by using thesecond pump (30), and the first oil that pressurized is as a second oiland supplied to the hydraulic operation part (56). When the second pump(30) is stopped in the second state, a control that gradually decreasesa target rotation speed (NA) of the second pump (30) is performed, andrates at which the target rotation speed (NA) of the second pump (30)decreases differ in a case where the second pump (30) is stopped in anoperation-allowed region and in a case where the second pump (30) isstopped when the second pump is determined as in an operation-disallowedregion.

In addition, it may be that, in such situation, compared with the casewhere the second pump (30) is stopped in the operation-allowed region,the rate at which the target rotation speed (NA) of the second pump (30)decreases is greater in the case where the second pump (30) is stoppedwhen the second pump (30) is determined as in the operation-disallowedregion.

In addition, in the hydraulic control device of the disclosure, it maybe that a determination on whether the second pump (30) is in theoperation-disallowed region is performed based on a size relationshipbetween a hydraulic pressure of dischargeable oil of the second pump(30) and a differential pressure between an estimated value of apressure value (PH) of oil supplied to the hydraulic operation part (56)and an estimated value of a pressure value (P3) of oil supplied from thefirst pump (20) to another hydraulic operation part (114) or alubrication target (108) which operates at a pressure lower than that ofthe hydraulic operation part (56).

In this case, it may be that the second pump (30) is determined as inthe operation-disallowed region in a case where the hydraulic pressureof the dischargeable oil of the second pump (30) is equal to or lessthan the differential pressure between the estimated value of thepressure value (PH) of the oil supplied to the hydraulic operation part(56) and the estimated value of the pressure value (P3) of the oilsupplied from the first pump (20) to the another hydraulic operationpart (114) or the lubrication target (108) which operates at thepressure lower than that of the hydraulic operation part.

In addition, the hydraulic control device may further include ahydraulic pressure sensor (26) that detects a pressure (P1) of oil on asucking side of the first oil in the second pump (30), and based on adetermination that an oil pressure (P1) detected by the hydraulicpressure sensor (26) has increased to a value substantially consistentwith the estimated value of the pressure value (PH) of the oil suppliedto the hydraulic operation part (56), the control that graduallydecreases the target rotation speed (NA) of the second pump (30) ends,and the target rotation speed (NA) of the second pump (30) is decreaseduntil a substantial stop rotation speed (N2).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a configuration diagram of a hydraulic control deviceaccording to an embodiment of the disclosure.

FIG. 2 is a configuration diagram of the line pressure adjusting valve.

In FIG. 3, (a) is a diagram showing an oil flow in a first state, and(b) is a diagram showing an oil flow in a second state.

FIG. 4 is a block diagram showing a calculating procedure of anestimated value of the line pressure.

FIG. 5 is a block diagram showing a calculating procedure of a targetrotation speed of the second pump.

FIG. 6 is a block diagram showing a calculating procedure of a targetrotation speed of the second pump in feedback control.

FIG. 7 is a timing chart for illustrating changes in each value in aservo state.

FIG. 8 is a graph showing regions where an operation of the second pumpis allowed/disallowed in a determination on a performance limit of thesecond pump.

FIG. 9 is a timing chart showing changes in each value in the controlthat stops the second pump when the second pump is determined as failed.

FIG. 10 is a timing chart showing changes in each value in the controlthat stops the second pump in an operation-allowed region.

FIG. 11 is a timing chart showing changes in each value in the controlthat stops the second pump when the second pump is in anoperation-disallowed region.

FIG. 12 is a diagram showing a relationship between a required oil flowrate in a continuously variable transmission mechanism and a performancelimit of the second pump.

FIG. 13 is a hydraulic pressure circuit diagram for outlining sidepressure correction control, where (a) is a case where the side pressurecorrection control is not performed, and (b) is a case where the sidepressure correction control is performed.

FIG. 14 is a block diagram showing a calculating procedure of acorrection hydraulic pressure in the side pressure correction control.

FIG. 15 is a diagram showing a map used for calculating a side pressurecorrection amount.

FIG. 16 is a timing chart showing changes in each value when the sidepressure correction control is performed.

DESCRIPTION OF THE EMBODIMENTS

According to the hydraulic control device of the disclosure, in the casewhere the second pump is stopped in the operation-allowed region, bymaking the rate at which the rotation speed of the second pump decreasessmaller, the fuel efficiency of the vehicle can be facilitated.Meanwhile, in the case where the second pump is determined as in theoperation-disallowed region, by making the rate at which the targetrotation speed of the second pump decreases greater than the rate in thecase where the second pump is stopped in the operation-allowed region,the rotation speed of the second pump can decrease earlier to ensure thehydraulic function of the hydraulic operation part. Accordingly, bymaking the rates at which the rotation speed of the second pumpdecreases different in the case where the second pump is stopped in theoperation-allowed region and the case where the second pump isdetermined as in the operation-disallowed region, the fuel efficiency ofthe vehicle can be facilitated, while the hydraulic function of thehydraulic operation part can be ensured.

In the case where the hydraulic pressure of the dischargeable oil of thesecond pump is equal to or less than the differential pressure betweenthe estimated value of the pressure value of the oil supplied to thehydraulic operation part and the estimated value of the pressure valueof the oil supplied from the first pump to the another hydraulicoperation part or the lubrication target which operates at the pressurelower than that of the hydraulic operation part, since the hydraulicpressure corresponding to the differential pressure cannot be covered bythe operation of the second pump, the concern that the energy efficiencycannot be improved through the operation of the second pump arises.Therefore, in such case, by determining the second pump as in theoperation-disallowed region, the control that stops the second pump isperformed at an earlier stage.

In the case where the oil pressure detected by the hydraulic pressuresensor is determined as having increased to a value substantiallyconsistent with the estimated value of the pressure value of the oilsupplied to the hydraulic operation part, the hydraulic pressurerequired by the hydraulic operation part can be covered by the operationof the first pump alone. Therefore, in such case, the control thatgradually decreases the target rotation speed of the second pump ends bydecreasing the target rotation speed of the second pump until thesubstantial stop rotation speed. Accordingly, the stop period of thesecond pump can be suitably determined, and it is possible to facilitatethe fuel efficiency.

The reference numerals in parentheses above indicate the drawingreference numbers of the corresponding components in the embodimentsdescribed later for reference.

According to the hydraulic control device of the disclosure, therotation speed at the time of stopping the second pump can be suitablycontrolled in response to the operation state of the second pump.

Hereinafter, embodiments of the disclosure will be described withreference to the accompanying drawings. FIG. 1 is a configurationdiagram of a hydraulic control device according to an embodiment of thedisclosure. A hydraulic control device 10 shown in FIG. 1 is applied to,for example, a vehicle 14 equipped with a transmission 12 which is acontinuously variable transmission (CVT).

The hydraulic control device 10 has a first pump (mechanical pump) 20that is driven by an engine 16 of the vehicle 14 and pumps up anddelivers oil (hydraulic oil) stored in a reservoir 18. An oil passage 22for flowing the oil pumped from the first pump 20 as a first oil isconnected to the output side of the first pump 20. A line pressureadjusting valve (pressure adjusting valve) 24, which is a spool valve,is provided in the middle of the oil passage 22.

In the oil passage 22, an output pressure sensor (P1 sensor) 26 isdisposed on the downstream side of the line pressure adjusting valve 24.The output pressure sensor 26 is a hydraulic sensor which sequentiallydetects the pressure (output pressure of the first pump 20) P1 of thefirst oil flowing through the oil passage 22, and which sequentiallyoutputs a detection signal indicating the detected output pressure P1 toa control unit 28 (to be described later). Further, a second pump 30having a capacity smaller than that of the first pump 20 is connected tothe downstream side of the oil passage 22.

The second pump 30 is an electric pump which is driven by the rotationof a motor 32 provided in the vehicle 14 and which outputs the first oilsupplied through the oil passage 22 as a second oil. In this case, thesecond pump 30 can pressurize the supplied first oil and pump thepressurized first oil as the second oil. The motor 32 rotates under thecontrol of a driver 34. The driver 34 controls the drive of the motor 32based on the control signal supplied from the control unit 28, andsequentially outputs a signal indicating the drive state of the motor 32(for example, the rotation speed Nem of the motor 32 according to therotation speed Nep of the second pump 30) to the control unit 28. Anelectric pump unit 36 is configured by the second pump 30, the motor 32,and the driver 34.

In addition, an ACG (alternating current generator) 40 is connected to acrankshaft 38 of the engine 16. The ACG 40 generates power by rotationof the crankshaft 38 due to the drive of the engine 16. The AC powergenerated by the ACG 40 is rectified by a rectifier 42 and charged intoa battery 44. The battery 44 is provided with a voltage sensor 46 whichdetects a voltage V of the battery 44 and a current sensor 48 whichdetects a current I flowing from the battery 44. The voltage sensor 46sequentially detects the voltage V of the battery 44, and sequentiallyoutputs a detection signal indicating the detected voltage V to thecontrol unit 28. The current sensor 48 sequentially detects the currentI flowing from the battery 44, and sequentially outputs a detectionsignal indicating the detected current I to the control unit 28. Thedriver 34 is driven by the power supply from the battery 44.

An oil passage 50 is connected to the output side of the second pump 30.The oil passage 50 is branched into two oil passages 50 a and 50 b onthe downstream side. One oil passage 50 a is connected to a drivenpulley 56 a, which configures a belt-type continuously variabletransmission mechanism 56 of the transmission 12 via a regulator valve52 a and an oil passage 54 a. The other oil passage 50 b is connected toa drive pulley 56 b configuring the continuously variable transmissionmechanism 56 via a regulator valve 52 b and an oil passage 54 b.

A bypass valve 58 is connected in parallel with the second pump 30between the two oil passages 22 and 50. The bypass valve 58 is a checkvalve provided so as to bypass the second pump 30, and allows the flowof oil (first oil) from the oil passage 22 on the upstream side to theoil passage 50 on the downstream side, while blocking the flow of oil(second oil) from the oil passage 50 on the downstream side to the oilpassage 22 on the upstream side.

Further, the oil passage 54 a is provided with a side pressure sensor 62as a hydraulic sensor for detecting the pressure PDN (the pulleypressure which is the side pressure of the driven pulley 56 a) of theoil supplied to the driven pulley 56 a.

A CR valve 64 is connected to the downstream side of an oil passage 50 cbranching from the oil passage 50. The upstream side of the CR valve 64is connected to the oil passage 50 c, and the downstream side thereof isconnected to two control valves 68 a and 68 b, a CPC valve 70 and an LCCvalve 72 via an oil passage 66. The CR valve 64 is a pressure reducingvalve which decompresses the oil (second oil) supplied from the oilpassage 50 c, and supplies the decompressed oil to the control valves 68a and 68 b, the CPC valve 70, and the LCC valve 72 via the oil passage66.

Each of the control valves 68 a and 68 b is a normally open typesolenoid valve having a solenoid, and is in a valve closed state whilethe control signal (current signal) is supplied from the control unit 28and the solenoid is energized, and is in a valve open state when thesolenoid is not energized.

One control valve 68 a is a solenoid valve for the driven pulley 56 a,and in the valve open state, the control valve 68 a supplies the oilsupplied from the CR valve 64 via the oil passage 66 to the regulatorvalve 52 a via an oil passage 74 a and also to the line pressureadjusting valve 24 via an oil passage 76 a (see FIG. 2). In FIG. 1, forconvenience, the oil passage 76 a is not shown.

Further, the other control valve 68 b is a solenoid valve for the drivepulley 56 b, and in the valve open state, the control valve 68 bsupplies the oil supplied from the CR valve 64 via the oil passage 66 tothe regulator valve 52 b via an oil passage 74 b and also to the linepressure adjusting valve 24 via an oil passage 76 b (see FIG. 2). Inaddition, the oil passage 76 b is also omitted in FIG. 1 forconvenience.

Therefore, in one regulator valve 52 a, the pressure of the oil suppliedfrom the control valve 68 a via the oil passage 74 a is used as a pilotpressure, and when the line pressure PH of the oil supplied via the oilpassages 50 and 50 a is greater than or equal to the predeterminedpressure, the valve is opened and the oil is supplied to the drivenpulley 56 a via the oil passage 54 a. Further, in the other regulatorvalve 52 b, the pressure of the oil supplied from the control valve 68 bvia the oil passage 74 b is used as a pilot pressure, and when the linepressure PH of the oil supplied via the oil passages 50 and 50 b isgreater than or equal to the predetermined pressure, the valve is in thevalve open state, and the oil is supplied to the drive pulley 56 b viathe oil passage 54 b.

In addition, the control valve 68 a can adjust the pressure of the oiloutput to the oil passages 74 a and 76 a. Further, the control valve 68b can adjust the pressure of the oil output to the oil passages 74 b and76 b.

The upstream side of the CPC valve 70 is connected to the oil passage66, and the downstream side thereof is connected to a manual valve 80via an oil passage 78. The CPC valve 70 is a solenoid valve for aforward clutch 82 a and a reverse brake clutch 82 b. In this case, whilethe control signal is supplied from the control unit 28 and the solenoidis energized, the CPC valve 70 is in the valve open state, and the oilpassages 66 and 78 are communicated with each other, and the oil issupplied to the manual valve 80.

The upstream side of the manual valve 80 is connected to the oil passage78, the downstream side thereof is connected to the forward clutch 82 avia an oil passage 84 a, and is connected to the reverse brake clutch 82b via an oil passage 84 b. The manual valve 80 is a spool valve, andwhen a driver operates a range selector 86 provided near the driver'sseat of the vehicle 14 to select any one of the shift ranges such as P(parking), R (reverse), N (neutral), and D (forward, drive), in themanual valve 80, a spool (not shown) moves for a predetermined amount inthe axial direction according to the selected shift range. In this way,the manual valve 80 enables the vehicle 14 to travel in the forwarddirection by supplying the oil supplied via the oil passage 78 to theforward clutch 82 a via the oil passage 84 a, or enables the vehicle 14to travel in the reverse direction by supplying the oil to the reversebrake clutch 82 b via the oil passage 84 b. A clutch pressure sensor 88for detecting the pressure (clutch pressure) of the oil supplied to theoil passage 84 a is provided in the middle of the oil passage 84 a.

A low-pressure hydraulic operation part to which the first oil issupplied via an oil passage 90 is connected to the oil passage 90 thatbranches from the oil passage 22 via the line pressure adjusting valve24. A TC regulator valve 104 and an oil warmer 106 are connected to thedownstream side of the oil passage 90 as the low-pressure hydraulicoperation part, and a lubrication system 108 of the transmission 12 isconnected as a lubrication target. The TC regulator valve 104 isconnected to the LCC valve 72 via an oil passage 110, and a torqueconverter 114 incorporating a lockup clutch 112 is connected to thedownstream side thereof.

The LCC valve 72 is a solenoid valve for the lockup clutch 112, andwhile the control signal is supplied from the control unit 28 and thesolenoid is energized, the LCC valve 72 is in the valve open state, andthe oil passages 66 and 110 are communicated with each other to supplythe oil to the TC regulator valve 104. The TC regulator valve 104 is aspool valve, and the spool (not shown) operates in the axial directionin response to the pressure of the oil supplied from the LCC valve 72via the oil passage 110, whereby a third oil supplied via the oilpassage 90 is decompressed, and the decompressed third oil is suppliedto the torque converter 114 and the lockup clutch 112.

The oil warmer 106 warms the third oil supplied from the oil passage 90to a predetermined temperature, and supplies the warmed third oil to apulley shaft 56 c, a bearing 56 d, and a belt 56 e that configure thecontinuously variable transmission mechanism 56. Further, thelubrication system 108 is various lubrication targets such as bearingsand gears that configure the transmission 12.

The hydraulic control device 10 further includes an engine rotationspeed sensor 116, an oil temperature sensor 118, a vehicle speed sensor120, an accelerator sensor 122, and the control unit 28. The enginerotation speed sensor 116 sequentially detects the engine rotation speedNew of the engine 16 according to the rotation speed Nmp of the firstpump 20, and sequentially outputs a detection signal indicating thedetected engine rotation speed New (rotation speed Nmp) to the controlunit 28. The oil temperature sensor 118 sequentially detects thetemperature (oil temperature) To of the first oil or the second oil, andsequentially outputs a detection signal indicating the detected oiltemperature To to the control unit 28. The vehicle speed sensor 120sequentially detects the vehicle speed Vs of the vehicle 14, andsequentially outputs a detection signal indicating the detected vehiclespeed Vs to the control unit 28. The accelerator sensor 122 sequentiallydetects the opening degree of an accelerator pedal (not shown) operatedby the driver, and sequentially outputs a detection signal indicatingthe detected opening degree to the control unit 28.

The control unit 28 is a microcomputer such as a CPU which functions asa TCU (transmission control unit) which controls the transmission 12 oran ECU (engine control unit) which controls the engine 16. Then, thecontrol unit 28 executes various controls on the hydraulic controldevice by reading and executing programs stored in a storage unit (notshown).

[Line Pressure Adjusting Valve 24]

FIG. 2 is a configuration diagram of the line pressure adjusting valve24. The line pressure adjusting valve 24 is a spool valve incorporatinga first spool 92 a and a second spool 92 b. The first spool 92 a is arelatively long valve body having a substantially I-shaped crosssection, and is disposed inside the line pressure adjusting valve 24along the axial direction (left-right direction in FIG. 2). The secondspool 92 b is a spool having a substantially Y-shaped cross section,which is shorter than the first spool 92 a, and is disposed inside theline pressure adjusting valve 24 on the right side of the first spool 92a along the axial direction. In this case, a first elastic member 94 ais inserted between the first spool 92 a and the second spool 92 b, andthe first elastic member 94 a urges the first spool 92 a to the leftdirection in FIG. 2. Further, the second spool 92 b is urged toward thefirst spool 92 a side by a second elastic member 94 b disposed on theright side of the second spool 92 b.

The line pressure adjusting valve 24 has first to seventh ports 96 a to96 g. The first port 96 a and the second port 96 b are provided so as toface each other at the central part of the outer peripheral surface ofthe line pressure adjusting valve 24. Further, the first port 96 a andthe second port 96 b are communicated with each other regardless of theposition of the first spool 92 a through a groove and the like (notshown) formed on the inner peripheral surface side of the line pressureadjusting valve 24 around the axial direction, and configures a part ofthe oil passage 22. In this case, the first port 96 a is an inlet portfor the first oil in the line pressure adjusting valve 24, and thesecond port 96 b is an outlet port for the first oil.

Then, with the position of the second port 96 b on the outer peripheralsurface of the line pressure adjusting valve 24 as the center, the thirdport 96 c and the fourth port 96 d are sequentially provided on the leftside of FIG. 2 so as to be separated from the second port 96 b, whilethe fifth to seventh ports 96 e to 96 g are sequentially provided on theright side of FIG. 2 so as to be separated from the second port 96 b.

The third port 96 c is provided adjacent to the left side of the secondport 96 b, and the oil passage 90 is connected to the third port 96 c.The fourth port 96 d is provided at the left end of the line pressureadjusting valve 24, and is connected to the oil passage 50 via an oilpassage 98. The fifth port 96 e is provided adjacent to the right sideof the second port 96 b, and is connected to the oil passage 50 via anoil passage 100. In addition, in FIG. 1, for convenience, the oilpassages 98 and 100 are not shown. The sixth port 96 f is provided onthe right side of the fifth port 96 e and is connected to the oilpassage 76 b. The seventh port 96 g is provided at the right end of theline pressure adjusting valve 24 and is connected to the oil passage 76a.

Therefore, oil (first oil or second oil) having the line pressure PHflowing through the oil passage 50 is supplied to the fourth port 96 dand the fifth port 96 e via the oil passages 98 and 100, respectively.Further, the oil is supplied from the control valve 68 b to the sixthport 96 f via the oil passage 76 b. Moreover, the oil is supplied fromthe control valve 68 a to the seventh port 96 g via the oil passage 76a.

On the outer peripheral surface of the first spool 92 a, by forminggrooves in the parts facing the first port 96 a and the second port 96 baround the axial direction, the part facing the first port 96 a isformed as a recess 102 a, and the part facing the second port 96 b isformed as a recess 102 b. Further, on the outer peripheral surface ofthe first spool 92 a, a recess 102 c adjacent to the recess 102 a and arecess 102 d adjacent to the recess 102 b are formed by forming groovesin the parts facing the third port 96 c around the axial direction.

Further, in the line pressure adjusting valve 24, the pressure (linepressure PH, output pressure P1) of the oil supplied to the fourth port96 d is greater than the pressure of the oil supplied to the sixth port96 f and the seventh port 96 g. However, since the oil contact areas ofthe valves are different, the pressures are balanced, and when the oilwith a pressure higher than the balance point is supplied to the fourthport 96 d, the first spool 92 a moves to the right side in FIG. 2 due tothe line pressure PH against the elastic force of the first elasticmember 94 a and the pressure of the oil supplied to the sixth port 96 f.As a result, the recess 102 c and the first port 96 a communicate witheach other, and the first oil can flow into the oil passage 90 via thefirst port 96 a, the recesses 102 c and 102 d, and the third port 96 c.Further, in the line pressure adjusting valve 24, the pressure of thefirst oil flowing through the oil passage 90 may be less than the outputpressure P1 of the first oil flowing through the second pump 30 and thebypass valve 58 via the oil passage 22. Therefore, in the followingdescription, the first oil flowing through the oil passage 90 may bereferred to as the third oil.

Next, the operation of the hydraulic control device 10 according to theembodiment configured as described above will be described. Here, a casewill be described in which the control unit 28 drives and controls thesecond pump 30 by performing the feedback control on the motor 32 mainlyusing the output pressure P1 of the first pump 20 or the line pressurePH (estimated value) (to be described later).

<Basic Operation of Hydraulic Control Device 10>

Prior to the description of the operation of the feedback control, thebasic operation of the hydraulic control device 10 will be described. Inthis basic operation, the operation of the hydraulic system whichsupplies the oil from the reservoir 18 to the continuously variabletransmission mechanism 56 via the first pump 20 and the like will bedescribed.

First, when the first pump 20 starts driving due to the drive of theengine 16, the first pump 20 pumps up the oil in the reservoir 18 andstarts pumping the pumped-up oil as the first oil. As a result, thefirst oil flows through the oil passage 22 via the first port 96 a andthe second port 96 b. The output pressure sensor 26 sequentially detectsthe pressure (output pressure) P1 of the first oil flowing through theoil passage 22, and outputs a signal indicating the detection result tothe control unit 28. Further, the engine rotation speed sensor 116sequentially detects the engine rotation speed New, and sequentiallyoutputs a signal indicating the detection result to the control unit 28.

In this case, since the motor 32 is not driven, the first oil flowingthrough the oil passage 22 flows to the oil passage 50 via the bypassvalve 58 along the line of the thick line, as schematically shown in (a)of FIG. 3. As a result, the first oil is supplied to the fourth port 96d via the oil passages 50 and 98, and is supplied to the fifth port 96 evia the oil passages 50 and 100, and is also supplied to the CR valve 64via the oil passages 50 and 50 c. The CR valve 64 decompresses thesupplied first oil, and supplies the decompressed first oil to thecontrol valves 68 a and 68 b via the oil passage 66, respectively.

Here, control signals (current values IDN, IDR) are supplied in advancefrom the control unit 28 to the solenoids of the control valves 68 a and68 b, and the control valves 68 a and 68 b are in the valve closedstate. Therefore, when the supply of the control signal to each solenoidis stopped, the control valves 68 a and 68 b are switched from the valveclosed state to the valve open state. As a result, the control valve 68a supplies the oil to the regulator valve 52 a via the oil passage 74 aand also supplies the oil to the seventh port 96 g via the oil passage76 a. Further, the control valve 68 b supplies the oil to the regulatorvalve 52 b via the oil passage 74 b and also supplies the oil to thesixth port 96 f via the oil passage 76 b.

The regulator valve 52 a uses the pressure of the oil supplied via theoil passage 74 a as the pilot pressure, and when the pressure of thefirst oil is greater than or equal to a predetermined pressure, theregulator valve 52 a is in a communication state, and the first oil issupplied to the driven pulley 56 a via the oil passage 54 a. The sidepressure sensor 62 sequentially detects the pressure (pulley pressurePDN, which is also the side pressure) of the first oil supplied to thedriven pulley 56 a, and sequentially outputs a signal indicating thedetection result to the control unit 28.

In addition, the regulator valve 52 b uses the pressure of the oilsupplied via the oil passage 74 b as the pilot pressure, and when thepressure (line pressure PH) of the first oil is greater than or equal toa predetermined pressure, the regulator valve 52 b is in a communicationstate, and the first oil is supplied to the drive pulley 56 b via theoil passage 54 b.

Further, in the line pressure adjusting valve 24, the first oil issupplied to the fourth port 96 d, and the oil is supplied from thecontrol valve 68 b to the sixth port 96 f, while the oil is alsosupplied from the control valve 68 a to the seventh port 96 g. In thiscase, since the pressure (line pressure PH, output pressure P1) of thefirst oil is greater than the pressure of the oil from each of thecontrol valves 68 a and 68 b, the first spool 92 a moves to the rightside in FIG. 2 due to the line pressure PH against the elastic force ofthe first elastic member 94 a and the pressure of the oil. As a result,the recess 102 c and the first port 96 a communicate with each other,and the first oil can be supplied to a low-pressure system such as thelubrication system 108 as the third oil via the first port 96 a, therecesses 102 c and 102 d, the third port 96 c, and the oil passage 90.

In this way, when a control signal is supplied from the control unit 28to the driver 34 in the state where the first pump 20 is being driven,the driver 34 drives the motor 32 based on the control signal and drivesthe second pump 30. As a result, the second pump 30 outputs the firstoil flowing through the oil passage 22 as the second oil.

Then, when the second oil flows through the oil passage 50 and the flowrate of the second oil (discharge flow rate of the second pump 30)exceeds the flow rate of the first oil (discharge flow rate of the firstpump 20), in the bypass valve 58, the pressure (line pressure PH) of theoil on the oil passage 50 side becomes greater than the pressure (outputpressure P1) of the oil on the oil passage 22 side. As a result, thebypass valve 58 is in the valve closed state, and the supply of thefirst oil from the first pump 20 to the continuously variabletransmission mechanism 56 and the like via the bypass valve 58 and theoil passage 50 as shown in (a) of FIG. 3 is switched to the supply ofthe second oil from the second pump 30 to the continuously variabletransmission mechanism 56 and the like via the oil passage 50 as shownby the thick line in (b) of FIG. 3. As a result, the flow of the firstoil to the oil passage 50 is blocked, and the second oil is pumped bythe second pump 30 to the continuously variable transmission mechanism56 and the like. The second oil is supplied to the fourth port 96 d viathe oil passages 50 and 98, is supplied to the fifth port 96 e via theoil passages 50 and 100, and is supplied to the CR valve 64. Further,the driver 34 sequentially outputs a signal indicating the motorrotation speed Nem of the motor 32 (rotation speed Nep of the secondpump 30) to the control unit 28.

The CR valve 64 decompresses the supplied second oil, and supplies thedecompressed second oil to the control valves 68 a and 68 b via the oilpassage 66, respectively. Since the control valve 68 a is in the valveopen state, it supplies the oil to the regulator valve 52 a via the oilpassage 74 a and also supplies the oil to the seventh port 96 g via theoil passage 76 a. Further, since the control valve 68 b is also in thevalve open state, it supplies the oil to the regulator valve 52 b viathe oil passage 74 b and also supplies the oil to the sixth port 96 fvia the oil passage 76 b.

As a result, the regulator valve 52 a supplies the second oil to thedriven pulley 56 a with the pressure of the oil supplied via the oilpassage 74 a as the pilot pressure. The side pressure sensor 62sequentially detects the pressure (side pressure PDN) of the second oilsupplied to the driven pulley 56 a and outputs it to the control unit28. In addition, the regulator valve 52 b supplies the second oil to thedrive pulley 56 b with the pressure of the oil supplied via the oilpassage 74 b as the pilot pressure.

In this way, since the pressurized second oil is supplied to the drivenpulley 56 a and the drive pulley 56 b, the pressure (output pressure) P1of the first oil can be reduced, and the load on the first pump 20 canbe reduced. In this case, the first spool 92 a moves to the right sidein FIG. 2 with the pressure (line pressure PH) of the second oilsupplied to the fourth port 96 d of the line pressure adjusting valve 24as the pilot pressure, and the output pressure P1 can be reduced byincreasing the opening degree (opening area) between the first port 96 aand the recess 102 c.

Further, in the line pressure adjusting valve 24, the oil is supplied tothe sixth port 96 f and the seventh port 96 g, respectively. In thiscase, since the line pressure PH is greater than the pressure of theoil, the first spool 92 a further moves to the right side in FIG. 2against the elastic force of the first elastic member 94 a and thepressure of the oil. As a result, when the recess 102 b and the fifthport 96 e communicate with each other, the oil passage 22 and the oilpassage 100 communicate with each other. As a result, an increase in thepressure (line pressure PH) of the second oil supplied to the oilpassage 100 is suppressed, and the line pressure PH can be maintained ata predetermined pressure.

Here, a state in which the second pump 30 is operated and the second oilis supplied from the second pump 30 will be described in detail. Inaddition, in the following description, the state in which the secondpump 30 is operated and the second oil is supplied from the second pump30 is referred to as a “servo state.”

Here, first, in describing the change of each value in the servo state,the calculation of the target rotation speed NA of the second pump 30 inthe servo state will be described. In the calculation of the targetrotation speed NA of the second pump 30, first, the control unit 28calculates the estimated value of the line pressure PH, and calculatesan estimated value of the pressure P3 of the third oil (hereinafterreferred to as “low hydraulic pressure”).

<Estimation of Line Pressure PH>

FIG. 4 is a block diagram showing a calculating procedure of anestimated value of the line pressure PH. The control unit 28 uses thecurrent value IDN, which is a control signal supplied to the solenoid ofthe control valve 68 a, and the current value IDR, which is a controlsignal supplied to the solenoid of the control valve 68 b, and refers tovarious maps stored in advance to calculate an estimated value of theline pressure PH.

The control unit 28 estimates the line pressure PH (estimated linepressure PH) according to a command value with the side pressure (pulleypressure) PDN or the like as the command value.

The side pressure PDN of the driven pulley 56 a is the pressure of theoil supplied from the oil passage 50 to the driven pulley 56 a via theoil passage 50 a, the regulator valve 52 a and the oil passage 54 a. Theside pressure PDN can be adjusted according to the pressure (pilotpressure) of the oil supplied from the control valve 68 a to theregulator valve 52 a via the oil passage 74 a. Further, the sidepressure PDR of the drive pulley 56 b is the pressure of the oilsupplied from the oil passage 50 to the drive pulley 56 b via the oilpassage 50 b, the regulator valve 52 b and the oil passage 54 b. Theside pressure PDR can be adjusted according to the pressure (pilotpressure) of the oil supplied from the control valve 68 b to theregulator valve 52 b via the oil passage 74 b.

Therefore, the control unit 28 refers to a 3D map stored in advance, andobtains an estimated value of the side pressure PDN (estimated sidepressure PDNe serving as a command value) according to the controlsignal (current value IDN) supplied to the solenoid of the control valve68 a. Further, the control unit 28 refers to a 3D map stored in advance,and obtains an estimated value of the side pressure PDR (estimated sidepressure PDRe serving as a command value) according to the controlsignal (current value IDR) supplied to the solenoid of the control valve68 b.

Each 3D map is a three-dimensional map showing the relationship betweenthe current values IDN and IDR and the estimated side pressures PDNe andPDRe generated for each oil temperature To of the first oil or thesecond oil. Therefore, the control unit 28 specifies the estimated sidepressures PDNe and PDRe according to the current oil temperature To andthe current values IDN and IDR from the 3D maps.

Next, the control unit 28 determines the higher hydraulic pressure valueof the two specified estimated side pressures PDNe and PDRe as a targetside pressure PDm. Next, the control unit 28 refers to a 1D map storedin advance, and specifies a target value PHt of the line pressure PHaccording to the target side pressure PDm. The 1D map is aone-dimensional map showing the relationship between the target sidepressure PDm and the line pressure PH.

Finally, the control unit 28 determines a value obtained by adding apredetermined amount of margin to the target value PHt as an estimatedvalue of the line pressure PH (estimated line pressure PH).

<Estimation of Low Hydraulic Pressure P3>

The control unit 28 refers to multiple maps corresponding to eachcomponent of the hydraulic system of the transmission 12 stored inadvance to estimate the pressure (low hydraulic pressure) P3 of thethird oil supplied to the TC regulator valve 104, the oil warmer 106,and the lubrication system 108 via the oil passage 90.

The characteristics of each component configuring the hydraulic systemof the transmission 12 are stored in advance as a map. Therefore, thecontrol unit 28 estimates the low hydraulic pressure P3 (estimated valueP3 e) by using the map of the characteristics of each component storedin advance.

Specifically, the control unit 28 estimates the pressure PCR of the oilpassing through the CR valve 64 by using the estimated value of the linepressure PH and the current value ICPC of the control signal supplied tothe CPC valve 70. In this case, the control unit 28 obtains the pressurePCR for each temperature and sets the obtained characteristics of thepressure PCR as a map.

Next, the control unit 28 estimates the pressure PLCC of the oil passingthrough the TC regulator valve 104 by using the map of the pressure PCRand the current value ILCC of the control signal supplied to thesolenoid of the LCC valve 72. The pressure PLCC is also the pressure ofthe oil supplied to the lockup clutch 112. In this case, the controlunit 28 obtains the pressure PLCC for each temperature and sets theobtained characteristics of the pressure PLCC as a map.

Next, the control unit 28 obtains the leakage amount of the hydraulicpath leading to the driven pulley 56 a and the drive pulley 56 b via theoil passages 50, 50 a and 50 b from the maps of the current values IDNand IDR and the side pressures PDN and PDR. Further, the control unit 28obtains the leakage amount of the LCC valve 72 from the map of thecurrent value ILCC, and obtains the leakage amount of the CR valve 64and the leakage amount of the CPC valve 70 from the map of the currentvalue ICPC.

Further, the control unit 28 calculates the flow rate (shift flow rateof the driven pulley 56 a and the drive pulley 56 b) of the second oilto be supplied to the continuously variable transmission mechanism 56during the shift operation from the area of the pulley chamber of thedriven pulley 56 a and the drive pulley 56 b and the rotation speed ofthe driven pulley 56 a and the drive pulley 56 b.

Then, the control unit 28 calculates the flow rate QPH of the oil to besupplied to the high-pressure hydraulic system from the second pump 30to the driven pulley 56 a and the drive pulley 56 b by adding theleakage amount of in the hydraulic path leading to the driven pulley 56a and drive pulley 56 b, the leakage amount of LCC valve 72, the leakageamount of CPC valve 70, the leakage amount of CR valve 64, the shiftflow rate, and the leakage amount of driven pulley 56 a and drive pulley56 b.

Next, the control unit 28 calculates the flow rate Q3 of the third oilsupplied to the low-pressure system via the oil passage 90 bysubtracting the flow rate QPH from the discharge flow rate of the firstoil from the first pump 20.

Next, the control unit 28 calculates an estimated value of the lowhydraulic pressure P3 according to the oil temperature To of the firstoil or the second oil based on the pressure PLCC of the oil passingthrough the TC regulator valve 104 and the flow rate Q3 of the thirdoil.

FIG. 5 is a block diagram showing a calculating procedure of the targetrotation speed NA of the second pump 30. In the calculation of thetarget rotation speed of the second pump 30, as shown in FIG. 5, arequired flow rate calculation part 153 calculates an oil flow rate(required flow rate) 154 required for the continuously variabletransmission mechanism 56, which is a hydraulic operation part, by usingan estimated value 151 of the line pressure PH and an oil temperature152 detected by the oil temperature sensor 118. Further, a differentialpressure calculation part 157 obtains an estimated value 158 of thedifferential pressure ΔP (=line pressure PH−low hydraulic pressure P3)by using an estimated value 155 of the line pressure PH and an estimatedvalue 156 of the low hydraulic pressure P3. Further, an F/B amountcalculation part 162 calculates a feedback amount 163 by using adetected value 159 of the output pressure P1 detected by the outputpressure sensor 26 and an estimated value 160 of the low hydraulicpressure P3. Then, an addition part 164 calculates an addition value 165by adding the feedback amount 163 to the calculated value 158 of thedifferential pressure ΔP, and a rotation speed calculation part 166calculates the target rotation speed NA of the second pump 30 by usingthis addition value 165 and the required flow rate 154.

The calculation of the feedback amount by the F/B amount calculationpart 162 will be described in detail. FIG. 6 is an illustrating diagramshowing processing in the control unit 28 which performs the feedbackcontrol with respect to the differential pressure ΔP by using the outputpressure P1 detected by the output pressure sensor 26. That is, FIG. 6is a control method for feedback-controlling the output pressure P1 withthe estimated value of the low hydraulic pressure P3 as the target valueby feeding back to the control unit 28 the change amount of the outputpressure P1 as the rotation speed of the second pump 30 increases.

When the estimated value of the line pressure PH is estimated and theestimated value of the low hydraulic pressure P3 is estimated, thecontrol unit 28 generates a command value ΔPi (=PHe−P3 e) of thedifferential pressure ΔP by subtracting the estimated value of the lowhydraulic pressure P3 from the estimated value of the line pressure PH.Further, the control unit 28 calculates an estimated value ΔPe (=PHe−P1)of the differential pressure ΔP by subtracting the output pressure P1detected by the output pressure sensor 26 from the estimated value ofthe line pressure PH.

Next, the control unit 28 obtains a deviation Ae (=ΔPi−ΔPe) bysubtracting the estimated value ΔPe from the command value ΔPi. Theobtained deviation Ae is passed through a proportional integrationelement (PI control) and added to the command value ΔPi. That is, thecontrol unit 28 performs the feedback control with the deviation Ae asthe feedback amount for the command value ΔPi.

In this case, Δe=ΔPi−ΔPe=(PHe−P3 e)−(PHe−P1)=P1−P3 e. Therefore, thecontrol unit 28 performs feedback control for the command value ΔPi sothat the output pressure P1 becomes an estimated value of the lowhydraulic pressure P3. Next, the control unit 28 adjusts the commandvalue ΔPi after the feedback control in consideration of the oiltemperature To of the first oil or the second oil as well. After that,the required flow rate Q and the adjusted command value ΔPi are used tocalculate the command value of the rotation speed for the second pump30.

FIG. 7 is a timing chart for illustrating changes in each value in theservo state. This timing chart shows the changes of the output pressureP1, the line pressure PH (estimated value), the low hydraulic pressureP3 (estimated value), the operation state (operational/stopped andoperation mode) of the second pump 30, the target rotation speed NA andthe actual rotation speed NB of the second pump 30 with respect to theelapsed time t.

In the timing chart of FIG. 7, the second pump 30 is stopped before thetime point t11. In this state, the first oil is supplied from the firstpump 20 to the continuously variable transmission mechanism 56 via thebypass valve 58 and the oil passage 50 (see (a) of FIG. 3). Therefore,the output pressure P1 which is the pressure of the first oil flowingthrough the oil passage 50 is equal to the line pressure PH (outputpressure P1=line pressure PH). Further, the low hydraulic pressure P3 isless than the line pressure PH and the output pressure P1 (line pressurePH>low hydraulic pressure P3, output pressure P1>low hydraulic pressureP3).

Then, when the second pump 30 operates at the time point t11, it is thenswitched to the supply of the second oil from the second pump 30 to thecontinuously variable transmission mechanism 56 via the oil passage 50(see (b) of FIG. 3). Therefore, after the state shown in (b) of FIG. 3is reached, the pressure of the second oil becomes the line pressure PH.

Here, the control unit 28 of the hydraulic control device 10 controlsthe motor 32 via the driver 34 so that the actual rotation speed NB ofthe second pump 30 (torque of the second pump 30) increases with respectto the elapsed time t. Accordingly, the flow rate of the second oildischarged from the second pump 30 gradually increases as the actualrotation speed NB of the second pump 30 increases. As a result, afterthe time point t11, the output pressure P1 can be gradually reduced withthe elapsed time t.

Then, in the operation state (servo state) of the second pump 30, thesecond pump 30 is operated by sequentially passing through each mode ofthe initial mode (INI mode), the feedback mode (F/B mode) and the fixedmode (FIX mode). In the initial mode, the target rotation speed NA ofthe second pump 30 increases at the time point t11, and the actualrotation speed NB gradually increases following the target rotationspeed NA. Further, in this initial mode, the target rotation speed NA ofthe second pump 30 is a rotation speed that can discharge only the flowrate required for consumption in the hydraulic operation part (targetrotation speed corresponding to only the required flow rate 154 in FIG.5). Therefore, the output pressure P1 does not decrease during theinitial mode. When it is determined that the actual rotation speed NB ofthe second pump 30 matches the target rotation speed NA, the initialmode ends.

In the feedback mode following the initial mode, the output pressure P1gradually decreases toward the low hydraulic pressure P3 as the actualrotation speed NB of the second pump 30 gradually increases. At the sametime, the feedback control of the rotation speed of the second pump 30is performed. That is, the control unit 28 performs the feedback controlof the rotation speed of the second pump 30 by using the output pressureP1 detected by the output pressure sensor 26, the estimated value of theline pressure PH, and the estimated value of the low hydraulic pressureP3. In this feedback mode, the output pressure P1 is feedback-controlledwith the low hydraulic pressure P3 as the target value by feeding backthe change amount of the output pressure P1 due to the increase in theactual rotation speed NB of the second pump 30 to the control unit 28.

As a result, for example, due to the error between the control value ofeach pressure and the actual pressure value and the variation in thedischarge performance of the second pump 30, even if the output pressureP1 cannot be reduced to the low hydraulic pressure P3 by using thetarget rotation speed of open control (the target rotation speedcorresponding to the calculated value 158 of the differential pressureΔP (=line pressure PH−low hydraulic pressure P3) shown in FIG. 5), inthe feedback mode after the time point t12, the output pressure P1 canbe reduced to the low hydraulic pressure P3 by using the target rotationspeed to which the feedback amount (F/B amount 163 in FIG. 5) is added.

When the feedback mode ends at the time point t13, the output pressureP1 drops till the low hydraulic pressure P3 at this time point (P1˜P3),and then the output pressure P1 is maintained at the low hydraulicpressure P3 (fixed mode). That is, in the fixed mode, the state of P1 P3is maintained by keeping the rotation speed of the second pump 30substantially constant. Then, when the operation of the second pump 30at a time point t14 stops, the target rotation speed NA of the secondpump 30 is changed to a stop rotation speed (≈0), and an actual rotationspeed [check] NB also decreases accordingly and gradually reaches thestop rotation speed. Accordingly, after the time point t14, the outputpressure P1 gradually increases toward the line pressure PH. Through theoperation of the second pump 30 as the above, in the state where theoutput pressure P1 decreases, the work load of the first pump 20 isreduced, and the fuel consumption of the vehicle 14 is improved.

Here, the operation condition of the second pump 30 is described. In thehydraulic control device of the embodiment, whether the operation of thesecond pump 30 is allowed/disallowed is determined based on a vehicletraveling state determination and a determination on the performancelimit of the second pump 30.

In the vehicle traveling state determination, specifically, in the casewhere, as the vehicle traveling state, for example, a shift command modeof the transmission (continuously variable transmission) being changedto a kick-down mode, a manual mode, a paddle mode, a change amount ofthe opening degree of the accelerator being equal to or greater than athreshold, a change amount of a ratio (actual ratio) of the transmissionbeing equal to or greater than a threshold, an indicative pressure ofthe drive pulley 56 b or the driven pulley 56 a being equal to orgreater than a threshold, a road surface on which the vehicle istraveling being a low friction coefficient road (low μ road), thevehicle spinning on ice, step shift being performed in the shift changeof the transmission, the operation of the second pump 30 is disalloweddue to the concern that the hydraulic pressure or the flow rate of thesecond pump 30 may become a high hydraulic pressure or a high flow rate.

In addition, in the determination on the performance limit of the secondpump 30, a determination is performed on whether the operation state ofthe second pump 30 is within an operable range where a state in whichthe output pressure P1 and the low hydraulic pressure P3 are equal(output pressure P1=low hydraulic pressure P3) can be realized. FIG. 8is a graph (map) showing regions where the operation of the second pump30 is allowed/disallowed in the determination on the performance limitof the second pump 30. In the graph of the same figure, the horizontalaxis represents the flow rate (required flow rate) of the second pump30, and the vertical axis represents the required hydraulic pressure(ΔP=line pressure PH−low hydraulic pressure P3) of the second pump 30.The graph (map) shows an example at a certain oil temperature. However,in reality, a plurality of different graphs (maps) are prepared for eachoil temperature. A region Y shown in FIG. 8 is a range where theoperation of the second pump 30 is allowed (operation-allowed region),and a region Z other than this region is a range where the operation ofthe second pump 30 is disallowed (operation-disallowed region). If thestate determined from the relationship between the required flow rateand the required hydraulic pressure is, for example, a state of a pointX1 of FIG. 8, the operation of the second pump 30 is allowed, and if thedetermined state is a state of a point X2, the operation of the secondpump 30 is disallowed.

Accordingly, in the case where the second pump 30 is in theoperation-disallowed region based on the vehicle traveling statedetermination and the determination on the performance limit of thesecond pump 30, the operation thereof is determined as disallowed.Therefore, in the case where the operation of the second pump 30 isdetermined as disallowed based on the vehicle traveling statedetermination or the determination on the performance limit of thesecond pump 30 in a state where the second pump 30 is operating, controlis performed to stop the operation of the second pump 30. Besides, inthe case where the second pump 30 is determined as failed in the statewhere the second pump 30 is operating, control is performed to stop thesecond pump 30. Besides, further to the above cases, in a normal vehicletraveling state, such as the case where the shift position of thetransmission is switched from a position for traveling forward to aposition for traveling backward or the case where the acceleratoropening degree is changed to 0, for example, control is also performedto stop the second pump 30. Therefore, the aspects for performingcontrol to stop the second pump 30 include three aspects, i.e., (1)stopping due to a failure of the second pump 30; (2) stopping in anoperation-allowed region; and (3) stopping in the case where the secondpump 30 is in the operation-disallowed region. In the following, thestop controls of the second pump 30 in the respective three aspects aredescribed in detail.

FIG. 9 is a timing chart showing changes in each value in the controlthat stops the second pump 30 when the second pump 30 is determined asfailed. The timing chart of the same figure shows the respective changesof a failure determination flag of the second pump 30, an operation flagof the second pump 30, flags for the target rotation speed NA and theactual rotation speed NB, the line pressure PH (estimated value), andthe output pressure P1, a flag for determination on the state(open/closed) of the bypass valve 58, a flag for determination onwhether the target rotation speed and the actual rotation speed of thesecond flag 30 are consistent with respect to a lapsed time t. FIGS. 10and 11 are the same in terms of the types of the values on the timingcharts.

In the control that stops the second pump 30 in the case where thesecond pump 30 is determined as failed, as shown in FIG. 9, bydetermining the second pump 30 as failed and changing the failuredetermination flag from 0 (normal) to 1 (failed) at a time point t31,the operation flag of the second pump 30 is changed from 1 (operational)to 0 (stopped). Accordingly, the target rotation speed NA of the secondpump 30 is changed to a stop rotation speed N2 (≈0). Here, it isnecessary to promptly stop the second pump 30 as the stop is due to afailure. Therefore, the target rotation speed NA of the second pump 30is directly changed to the stop operation speed N2 at the time pointt31. Accordingly, since the time point t31, the actual rotation speed NBof the second pump 30 decreases gradually. Meanwhile, the outputpressure P1 gradually increases. At a time point t32, by determiningthat the output pressure P1 has increased till a value substantiallyconsistent with the line pressure PH, the state of the bypass valve 58is determined as being changed from a closed state to an open state. Thedetermination that the output pressure P1 has increased till the valuesubstantially consistent with the line pressure PH is a determinationmade based on that the output pressure P1 exceeds a hydraulic pressurepredetermined value U1 less than the estimated value of the linepressure PH by a predetermined amount. Then, with the actual rotationspeed NB of the second pump 30 being changed to the stop rotation speedN2 at the time point t32, the target rotation speed NA is determined asconsistent with the actual rotation speed NB. In the control that stopsthe second pump 30 in the case where the second pump 30 is determined asfailed, a compulsory timer TM1 for stopping the second pump 30 at thetime point 31 is operated. The compulsory timer TM1 is one provided forthe sake of safety, and is one that compulsorily stops the second pump30 in the case where the actual rotation speed of the second pump 30 hasnot decreased to the stop rotation speed N2 (the case where the targetrotation speed NA has not been determined as consistent with the actualrotation speed NB) at a time point at which the compulsory timer TM1completes the countdown.

FIG. 10 is a timing chart showing changes in each value in the controlthat stops the second pump 30 in the operation-allowed region. In thecontrol that stops the second pump 30 in the operation-allowed region,as shown in the same figure, the stop of the second pump 30 isdetermined at a time point t41, and the operation flag of the secondpump is changed from 1 (operational) to 0 (stopped). Accordingly, sincethe time point t41, the target rotation speed NA of the second pump 30decreases gradually. Here, the rate (slope) at which the target rotationspeed NA decreases is a rate (slope) smaller than stopping in the casewhere the second pump 30 is in the operation-disallowed region, whichwill be described afterwards. Then, as the target rotation speed NAdecreases, the actual rotation speed NB also decreases. In addition, atthe time point t41, the compulsory timer TM1 also operates. Then, at atime point t42, when the output pressure P1 is determined as havingincreased to a value substantially consistent with the line pressure PHby exceeding a hydraulic pressure predetermined value U2 less than theestimated value of the line pressure PH by a predetermined amount, thecountdown of a timer TM2 starts. At a time point t43, with the timer TM2completing the countdown, the state of the bypass valve 58 is determinedas being changed from the closed state to the open state. Meanwhile, thetarget rotation speed NA of the second pump 30 decreases to the standbyrotation speed N1. Here, the standby rotation speed N1 is a valuesomewhat greater than the stop rotation speed N2, and is the lowestrotation speed at which the second pump 30 substantially does not stop.Here, the reason for setting the standby rotation speed N1 is that, bygoing through the standby rotation speed N1, that the actual rotationspeed NB follows the stop rotation speed can be confirmed before beingshifted to the stop rotation speed N2, so the actual rotation speed NBcan more stably decrease to the stop rotation speed N2.

Then, the actual rotation speed NB of the second pump 30 graduallydecreases toward the target rotation speed NA, and at a time point t44,with the actual rotation speed NB of the second pump 30 decreasing tillor lower than a predetermined rotation speed N3, which is a valuegreater than the target rotation speed NA by a predetermined amount, atimer TM3 operates. At a time point t45, the timer TM3 completes thecountdown to decrease the target rotation speed NA till the stoprotation speed N2 (≈0). In addition, at this time point, the targetrotation speed NA and the actual rotation speed NB are determined asconsistent. The determination of being consistent is made under theconditions that a difference between the actual rotation speed NB of thesecond pump 30 and the standby rotation speed NB becomes equal to orless than the predetermined rotation speed N3 and the timer TM3 whichstarts to count down from the time point completes the countdown.

Accordingly, in the case where the second pump 30 is stopped in theoperation-allowed region, control that gradually decreases the targetrotation speed NA of the second pump 30 is performed. Then, thedecreasing rate (slope) is a rate (slope) smaller than the case wherethe second pump 30 is in the operation-disallowed region, which will bedescribed afterwards. This is because, compared with the case ofdrastically stopping the second pump 30, gradually decreasing therotation speed of the second pump 30 and decreasing at a smaller ratecan facilitate the fuel efficiency of the vehicle by suppressing thedrastic decrease of the hydraulic pressure supplied to the hydraulicoperation part, such as the continuously variable transmission mechanism56, through the operation of the second pump 30. In addition, there is acase where a return (restart) command of the second pump 30 is receivedbetween the stop command of the second pump 30 and the actual stop. Theabove also allows the second pump 30 to return quickly in this case.

FIG. 11 is a timing chart showing changes in each value in the controlthat stops the second pump 30 when the second pump 30 is in theoperation-disallowed region. In the control that stops the second pump30 in the case where the second pump 30 is in the operation-disallowedregion, as shown in the same figure, the second pump 30 is determined asin the operation-disallowed region at a time point t51, and anoperation-disallowed region determination flag is changed from 1 (withinregion) to 0 (out of region). Together with this, at a time point t52,the stop of the second pump 30 is determined, the second pump operationflag is changed from 1 (operational) to 0 (stopped). Accordingly, sincethe time point t52, the target rotation speed NA of the second pump 30decreases gradually. The decreasing rate here is a rate (slope) greaterthan the case where the second pump 30 is stopped in theoperation-allowed region of FIG. 10. Then, as the target rotation speedNA decreases, the actual rotation speed NB also decreases. In addition,at the time point t52, the compulsory timer TM1 also operates. Then,with the output pressure P1 exceeding a hydraulic pressure predeterminedvalue U3, which is a value less than the estimated value of the linepressure PH by a predetermined amount, at a time point t53, the timerTM2 operates. At a time point t54, the timer TM2 completes the countdownand, with the output pressure P1 having increased till a valuesubstantially consistent with the line pressure PH, the statedetermination of the bypass valve 58 is changed from the closed state tothe open state. Meanwhile, the target rotation speed NA of the secondpump 30 decreases to the standby rotation speed N1. Here, the standbyrotation speed N1 is a value somewhat greater than the stop rotationspeed N2, and is the lowest rotation speed at which the second pump 30substantially does not stop. Then, the actual rotation speed NB of thesecond pump 30 gradually decreases toward the target rotation speed NA,and with the actual rotation speed NB of the second pump 30 decreasingtill or lower than the predetermined rotation speed N3, which is a valuegreater than the target rotation speed NA by a predetermined amount, ata time point t55, the timer TM3 operates, and the timer TM3 elapses todecrease the target rotation speed NA till the stop rotation speed N2(≈0) at a time point t56. In addition, at this time point, the targetrotation speed and the actual rotation speed are determined asconsistent. The determination of being consistent, like the case ofstopping in the operation-allowed region of FIG. 10, is made under theconditions that the difference between the actual rotation speed NB ofthe second pump 30 and the standby rotation speed NB becomes equal to orless than the predetermined rotation speed N3 and the timer TM3 whichstarts to count down from the time point completes the countdown. Then,the actual rotation speed NB of the second pump 30 decreases toward thetarget rotation speed NA (stop rotation speed N2), and the second pump30 stops.

Here, the change rate (slope) of the target rotation speed NA during thegradual decrease of the target rotation speed NA of the second pump 30from the time point t52 to the time point t53 in the control that stopsthe second pump 30 in the case where the second pump 30 is in theoperation-disallowed region as shown in FIG. 11 is a change rate (slope)greater than the change rate (slope) of the target rotation speed NAduring the gradual increase of the target rotation speed NA of thesecond pump 30 from the time point t41 to the time point t42 in thecontrol that stops the second pump 30 in the operation-allowed regionshown in FIG. 10. This is because, in the case where the second pump 30is in the operation-disallowed region, it is necessary to ensure(secure) the required hydraulic pressure in the hydraulic operationpart, such as the continuously variable transmission mechanism 56, bystopping the second pump 30 more quickly than in the operation-allowedregion.

Moreover, in the case of the operation-allowed region shown in FIG. 10and the case of being in the operation-disallowed region as shown inFIG. 11, gradually decreasing, instead of decreasing the target rotationspeed NA till the stop rotation speed N2 (≈0) (at once) in the casewhere the second pump 30 fails as shown in FIG. 9, is carried outbecause when the target rotation speed NA of the second pump 30 isdirectly set to the stop rotation speed N2 (≈0) from the servo state,during the process of ending the servo state (process of transitioningfrom the first state to the second state), as shown by a dotted linerepresented by a symbol A of FIG. 7, the phenomenon that the linepressure PH (the hydraulic pressure of the oil supplied to thecontinuously variable transmission mechanism 56) decreases temporarilymay occur. Consequently, the control for suppressing the amount of thedecrease of the line pressure to a small amount as much as possible iscarried out.

Accordingly, in the hydraulic control device, when the second pump 30 isstopped to switch from the second state to the first state, there is aconcern that the phenomenon in which the line pressure PH (hydraulicpressure of the oil supplied to the continuously variable transmissionmechanism 56) drops temporarily may occur, as shown by the dotted linerepresented by the symbol A of FIG. 7.

Therefore, in the embodiment, as the control for preventing the decrease(decrease in side pressure) of the hydraulic pressure (pulley sidepressure) supplied to the continuously variable transmission mechanism56 due to such temporary decrease of the line pressure PH, in additionto the control of gradually decreasing the rotation speed of the secondpump 30 as the above, control that adds a correction hydraulic pressureof a predetermined amount to the hydraulic pressure supplied to thedriven pulley 56 a of the continuously variable transmission mechanism56 is performed. In the following, such control is referred to as “sidepressure correction control”. In the following, the side pressurecorrection control is described.

The side pressure correction control is implemented in the case wherethe operation of the second pump 30 is determined as disallowed based onthe determination on the performance limit of the second pump 30described above. That is, the relationship between the flow rate of thesecond pump 30 and the differential pressure is implemented in the casewhere the region falls out of the region U shown in FIG. 8. FIG. 12 is adiagram showing the relationship between the flow rate (required flowrate) of the oil required in the continuously variable transmissionmechanism (CVT) 56 and the performance limit (of the discharge amount)of the second pump 30, where (a) of FIG. 12 shows the case where therequired flow rate of the continuously variable transmission mechanism56 is lower than the performance limit of the second pump 30, and (b) ofFIG. 12 shows the case where the required flow rate of the continuouslyvariable transmission mechanism 56 is higher than the performance limitof the second pump 30. In the region (region Y of FIG. 8) where theoperation of the second pump 30 is allowed based on the determination onthe performance limit, as shown in (a) of FIG. 12, the flow rate of theoil required in the continuously variable transmission mechanism 56 islower than the performance limit of the second pump 30. Meanwhile, inthe region (region other than the region Y of FIG. 8) where theoperation of the second pump 30 is determined as disallowed, as shown in(b) of FIG. 12, the flow rate of the oil required in the continuouslyvariable transmission mechanism 56 is higher than the performance limitof the second pump 30. Therefore, in the region other than the region Y,since the flow rate of the oil required in the continuously variabletransmission mechanism 56 cannot be supplied through the operation ofthe second pump 30, it is necessary to make corresponding compensationfor the flow rate/hydraulic pressure of the oil through the sidepressure correction control.

Since the side pressure correction control is performed in the casewhere the operation of the second pump 30 is determined as disallowedbased on the determination on the performance limit of the second pump30, the control for the case where the second pump 30 is in theoperation-disallowed region as shown in FIG. 11 is performed as thecontrol that stops the second pump 30 in this case.

FIG. 13 is diagram showing a portion of a hydraulic pressure circuitdiagram for outlining the side pressure correction control, where (a) isa case where the side pressure correction control is not performed, and(b) is a case where the side pressure correction control is performed.As shown in (a) of the same figure, the flow of the phenomenon thatoccurs when the second pump 30 is stopped is as follows. (1-1) Therotation speed of the second pump 30 decreases. (1-2) The line pressurePH decreases, and the flow rate of the oil flowing into the fourth port96 d and the fifth port 96 e of the line pressure adjusting valve 24decreases. (1-3) The first spool 92 a of the line pressure adjustingvalve 24 is moved toward the left of the figure. (1-4) The third port 96c of the line pressure adjusting valve 24 is closed, and the outputpressure P1 of the first pump 20 increases. (1-5) The bypass valve 58 isopened, and the second state is switched to the first state. Asdescribed above, between (1-1) where the rotation speed of the secondpump 30 decreases and (1-4) where the third port 96 c of the pressureadjusting valve is closed and the output pressure P1 increases, that is,in a responding (restoring) process of the output pressure P1, theconcern that the line pressure PH decreases arises.

Meanwhile, the flow in the case where the side pressure correctioncontrol is performed is as follows. (2-1) The rotation speed of thesecond pump 30 decreases. (2-2) The side pressure correction control isimplemented. (2-3) The first spool 92 a of the line pressure adjustingvalve 24 is moved toward the left of the figure. (2-4) The third port 96c of the line pressure adjusting valve 24 is closed, and the outputpressure P1 of the first pump 20 increases. (2-5) The bypass valve 58 isopened, and the second state is switched to the first state.Accordingly, at the timing of (2-1) where the rotation speed of thesecond pump 30 decreases, the side pressure correction control of (2-2)is implemented. Accordingly, the decrease of the line pressure PH thatoccurs in (1-2) in (a) of FIG. 13 does not occur and is remedied.Therefore, between (2-1) where the rotation speed of the second pump 30decreases and (2-4) where the third port 96 c of the pressure adjustingvalve is closed and the output pressure P1 increases, that is, in theresponding (restoring) process of the output pressure P1, the linepressure PH can be prevented from decreasing.

Specifically, with the side pressure correction control described hereinby changing the indicative oil value with respect to the control valve68 a, the correction hydraulic pressure is added to the hydraulicpressure supplied from the control valve 68 a to the regulator valve 52a. Then, since a portion of the hydraulic pressure supplied from thecontrol valve 68 a to the regulator valve 52 a is also supplied to theline pressure adjusting valve 24, a portion of the correction hydraulicpressure added in the side pressure correction control is supplied tothe line pressure adjusting valve 24 via the seventh port 96 g. Thehydraulic pressure urges the first spool 92 a and the second spool 92 bof the line pressure adjusting valve 24 to the left direction of thefigure. Therefore, in (2-3) above, the first spool 92 a can be morequickly moved leftward. Accordingly, with the opening degree (openingarea) between the first port 96 a and the recess 102 c being reduced atan early stage, the output pressure P1 can be more quickly restored.Therefore, the decrease of the line pressure PH (decrease of sidepressure) can be prevented as a consequence.

FIG. 14 is a block diagram showing a calculating procedure of thecorrection hydraulic pressure in the side pressure correction control.Here, a side pressure correction amount calculation part 203 uses anestimated value 201 of the line pressure PH and a ratio 202 of thecontinuously variable transmission mechanism 56 to calculate a sidepressure correction amount (torque). The side pressure correction amount(torque) is calculated by using a three-dimensional map showing arelationship between the side pressure correction amount and the linepressure (estimated value) generated for each ratio, as shown in FIG.15, and searching for a value on the three-dimensional map. Then, thevalue of the input torque is determined by taking into account a sidepressure correction implementation determination result by a sidepressure correction implementation determination part 204 with respectto the calculated side pressure correction amount. The side pressurecorrection implementation determination result taken into account by theside pressure correction implementation part 204 is the resultdetermined under the conditions shown in FIGS. 8 and 12 and thedescriptions thereof. Then, a required thrust is calculated by a pulleythrust calculation part 205 from the determined value of the inputtorque, and the value of the required hydraulic pressure is calculatedby a pulley hydraulic pressure calculation part 206 from the value ofthe required thrust.

FIG. 16 is a timing chart showing changes in each value when the sidepressure correction control is performed. In the timing chart of thesame figure, the respective changes of the target rotation speed NA andthe actual rotation speed NB of the second pump 30, the side pressurecorrection amount M, the line pressure PH, and the output pressure P1 ofthe first pump 20 over time are shown. Here, at the time point t14(corresponding to the time point t14 of FIG. 7), by changing the targetrotation speed NA of the second pump 30 to the stop rotation speed N2(≈0), the actual rotation speed NB gradually decreases since then. Then,at the time point t14, the side pressure correction amount M is changedfrom 0 to a predetermined value M1. The predetermined value M1 is avalue calculated in FIG. 14 and the procedure shown and describedtherein. Then, between the time points t14 and t15, the actual rotationspeed NB of the second pump 30 gradually decreases, whereas the outputpressure P1 gradually increases to approach the line pressure PH.Afterwards, the side pressure correction control ends at the time pointt15. The time point at which the side pressure correction control endsis determined by the stop of the second pump 30 and the opening of thebypass valve 58. That is, if the second pump 30 stops, the operationstate of the second pump 30 does not shift (restore), so the sidepressure correction control ends.

Further, the side pressure correction amount is controlled to be kept ata constant value (predetermined value MD during the period when the sidepressure correction control is implemented, such as between the timepoint t14 and the time point t15 in FIG. 16. This is because that,assuming that the side pressure correction amount decreases in the statein which the second pump 30 is rotating in the implementation of theside pressure correction control, the first spool 92 a of the linepressure adjusting valve 24 shown in FIG. 2 is pushed to the right sideof the figure to open the third port 96 c and discharge oil via the oilpassage 90. Accordingly, the output pressure P1 decreases to return tothe operation state of the second pump 30, which needs to be prevented.

As described above, according to the hydraulic control device of theembodiment, the bypass valve 58 and the second pump 30 driven by themotor 32 are connected in parallel between the first pump 20 and thehydraulic operation part, such as the continuously variable transmissionmechanism 56. In the hydraulic control device switchable between thefirst state in which the first oil is supplied from the first pump 20 tothe hydraulic operation part via the bypass valve 58 and the secondstate in which the first oil supplied from the first pump 20 ispressurized by using the second pump 30 and the pressurized first oil issupplied, as the second oil, to the hydraulic operation part, when thesecond pump 30 is stopped in the second state, the control thatgradually decreases the target rotation speed NA of the second pump 30is performed, and the rates at which the target rotation speed NA of thesecond pump 30 decreases differ in the case where the second pump 30 isstopped in the operation-allowed region and in the case where the secondpump 30 is stopped when the second pump 30 is determined as in theoperation-disallowed region.

In addition, in such situation, compared with the case where the secondpump 30 is stopped in the operation-allowed region, the rate at whichthe target rotation speed NA of the second pump 30 decreases is greaterin the case where the second pump 30 is stopped when the second pump 30is determined as in the operation-disallowed region.

According to the hydraulic control device of the embodiment, in the casewhere the second pump 30 is stopped in the operation-allowed region, bymaking the rate at which the rotation speed of the second pump 30decreases smaller, the fuel efficiency of the vehicle can befacilitated. Meanwhile, in the case where the second pump 30 isdetermined as in the operation-disallowed region, by making the rate atwhich the target rotation speed NA of the second pump 30 decreasesgreater than the rate in the case where the second pump 30 is stopped inthe operation-allowed region, the rotation speed of the second pump 30can decrease earlier to ensure the hydraulic function of the hydraulicoperation part. Accordingly, by making the rates at which the rotationspeed of the second pump 30 decreases different in the case where thesecond pump 30 is stopped in the operation-allowed region and the casewhere the second pump 30 is determined as in the operation-disallowedregion, the fuel efficiency of the vehicle can be facilitated, while thehydraulic function of the hydraulic operation part can be ensured.

In addition, in the hydraulic control device of the embodiment, adetermination on whether the second pump 30 is in theoperation-disallowed region is performed based on a size relationshipbetween a hydraulic pressure of dischargeable oil of the second pump 30and a differential pressure between the estimated value of the linepressure PH, which is a pressure value of the oil supplied to thehydraulic operation part such as the continuously variable transmissionmechanism 56, and an estimated value of the low hydraulic pressure P3,which is a pressure value of the oil supplied from the first pump 20 tothe torque converter 114, which is another hydraulic operation part, orthe lubrication system 108 which operates at a lower pressure. In thecase where the hydraulic pressure of the dischargeable oil of the secondpump is equal to or less than the differential pressure between theestimated value of the line pressure PH and the estimated value of thelow hydraulic pressure P3, the second pump 30 is determined as in theoperation-disallowed region.

In the case where the hydraulic pressure of the dischargeable oil of thesecond pump is equal to or less than the differential pressure betweenthe estimated value of the line pressure PH and the estimated value ofthe low hydraulic pressure P3, since the hydraulic pressurecorresponding to the differential pressure cannot be covered by theoperation of the second pump 30, the concern that the energy efficiencycannot be improved through the operation of the second pump 30 arises.Therefore, in such case, by determining the second pump 30 as in theoperation-disallowed region, the control that stops the second pump 30is performed at an earlier stage.

In addition, the hydraulic control device of the embodiment may furtherincludes the output pressure sensor 26 that detects the output pressureP1, which is a pressure of oil on a sucking side of the first oil in thesecond pump 30, and based on a determination that the output pressure P1detected by the output pressure sensor 26 has increased to a valuesubstantially consistent with the estimated value of the line pressurePH, which is the pressure value of the oil supplied to the hydraulicoperation part such as the continuously variable transmission mechanism56, the control that gradually decreases the target rotation speed NA ofthe second pump 30 ends, and the target rotation speed NA of the secondpump 30 is decreased until the substantial stop rotation speed N2.

In the case where the output pressure P1 detected by the output pressuresensor 26 is determined as having increased to a value substantiallyconsistent with the estimated value of the line pressure PH supplied tothe hydraulic operation part, the hydraulic pressure required by thehydraulic operation part can be covered by the operation of the firstpump 20 alone. Therefore, in such case, the control that graduallydecreases the target rotation speed NA of the second pump 30 ends bydecreasing the target rotation speed NA of the second pump 30 until thesubstantial stop rotation speed N2. Accordingly, the stop period of thesecond pump 30 can be suitably determined, and it is possible tofacilitate the fuel efficiency.

Although the embodiments of the disclosure have been described above,the disclosure is not limited to the above embodiments, and variousmodifications can be made within the scopes of claims and the technicalconcepts described in the specification and drawings. For example, ifthe control that gradually decreases the target rotation speed of thesecond pump in the disclosure is the control that decreases the targetrotation speed through time, the exact example of the decrease is notlimited to the above embodiment, and various examples may be adopted.That is, it suffices as long as the target rotation speed is constantlylower than before in the interval between the start point and the endpoint of the control. The specific embodiment is not limited to the onein which the target rotation speed decreases linearly through time, butmay also be one in which the target rotation speed decreases in stages,or a combination thereof.

What is claimed is:
 1. A hydraulic control device, wherein a bypassvalve and a second pump driven by a motor are connected in parallelbetween a first pump and a hydraulic operation part of a transmission,the hydraulic control device is configured to be switchable between afirst state and a second state, wherein in the first state, a first oilis supplied from the first pump to the hydraulic operation part via thebypass valve, and in the second state, the first oil supplied from thefirst pump is pressurized by using the second pump, and the first oilthat is pressurized is as a second oil and supplied to the hydraulicoperation part, wherein when the second pump is stopped in the secondstate, a control that gradually decreases a target rotation speed of thesecond pump is performed, and rates at which the target rotation speedof the second pump decreases differ in a case where the second pump isstopped in an operation-allowed region and in a case where the secondpump is stopped when the second pump is determined as in anoperation-disallowed region.
 2. The hydraulic control device as claimedin claim 1, wherein compared with the case where the second pump isstopped in the operation-allowed region, the rate at which the targetrotation speed of the second pump decreases is greater in the case wherethe second pump is stopped when the second pump is determined as in theoperation-disallowed region.
 3. The hydraulic control device as claimedin claim 1, wherein a determination on whether the second pump is in theoperation-disallowed region is performed based on a size relationshipbetween a hydraulic pressure of dischargeable oil of the second pump anda differential pressure between an estimated value of a pressure valueof oil supplied to the hydraulic operation part and an estimated valueof a pressure value of oil supplied from the first pump to anotherhydraulic operation part or a lubrication target which operates at apressure lower than that of the hydraulic operation part.
 4. Thehydraulic control device as claimed in claim 2, wherein a determinationon whether the second pump is in the operation-disallowed region isperformed based on a size relationship between a hydraulic pressure ofdischargeable oil of the second pump and a differential pressure betweenan estimated value of a pressure value of oil supplied to the hydraulicoperation part and an estimated value of a pressure value of oilsupplied from the first pump to another hydraulic operation part or alubrication target which operates at a pressure lower than that of thehydraulic operation part.
 5. The hydraulic control device as claimed inclaim 3, wherein the second pump is determined as in theoperation-disallowed region in a case where the hydraulic pressure ofthe dischargeable oil of the second pump is equal to or less than thedifferential pressure between the estimated value of the pressure valueof the oil supplied to the hydraulic operation part and the estimatedvalue of the pressure value of the oil supplied from the first pump tothe another hydraulic operation part or the lubrication target whichoperates at the pressure lower than that of the hydraulic operationpart.
 6. The hydraulic control device as claimed in claim 4, wherein thesecond pump is determined as in the operation-disallowed region in acase where the hydraulic pressure of the dischargeable oil of the secondpump is equal to or less than the differential pressure between theestimated value of the pressure value of the oil supplied to thehydraulic operation part and the estimated value of the pressure valueof the oil supplied from the first pump to the another hydraulicoperation part or the lubrication target which operates at the pressurelower than that of the hydraulic operation part.
 7. The hydrauliccontrol device as claimed in claim 1, further comprising: a hydraulicpressure sensor, detecting a pressure of oil on a sucking side of thefirst oil in the second pump, and based on a determination that an oilpressure detected by the hydraulic pressure sensor has increased to avalue substantially consistent with the estimated value of the pressurevalue of the oil supplied to the hydraulic operation part, the controlthat gradually decreases the target rotation speed of the second pumpends, and the target rotation speed of the second pump is decreaseduntil a substantial stop rotation speed.
 8. The hydraulic control deviceas claimed in claim 2, further comprising: a hydraulic pressure sensor,detecting a pressure of oil on a sucking side of the first oil in thesecond pump, and based on a determination that an oil pressure detectedby the hydraulic pressure sensor has increased to a value substantiallyconsistent with the estimated value of the pressure value of the oilsupplied to the hydraulic operation part, the control that graduallydecreases the target rotation speed of the second pump ends, and thetarget rotation speed of the second pump is decreased until asubstantial stop rotation speed.
 9. The hydraulic control device asclaimed in claim 3, further comprising: a hydraulic pressure sensor,detecting a pressure of oil on a sucking side of the first oil in thesecond pump, and based on a determination that an oil pressure detectedby the hydraulic pressure sensor has increased to a value substantiallyconsistent with the estimated value of the pressure value of the oilsupplied to the hydraulic operation part, the control that graduallydecreases the target rotation speed of the second pump ends, and thetarget rotation speed of the second pump is decreased until asubstantial stop rotation speed.
 10. The hydraulic control device asclaimed in claim 4, further comprising: a hydraulic pressure sensor,detecting a pressure of oil on a sucking side of the first oil in thesecond pump, and based on a determination that an oil pressure detectedby the hydraulic pressure sensor has increased to a value substantiallyconsistent with the estimated value of the pressure value of the oilsupplied to the hydraulic operation part, the control that graduallydecreases the target rotation speed of the second pump ends, and thetarget rotation speed of the second pump is decreased until asubstantial stop rotation speed.
 11. The hydraulic control device asclaimed in claim 5, further comprising: a hydraulic pressure sensor,detecting a pressure of oil on a sucking side of the first oil in thesecond pump, and based on a determination that an oil pressure detectedby the hydraulic pressure sensor has increased to a value substantiallyconsistent with the estimated value of the pressure value of the oilsupplied to the hydraulic operation part, the control that graduallydecreases the target rotation speed of the second pump ends, and thetarget rotation speed of the second pump is decreased until asubstantial stop rotation speed.
 12. The hydraulic control device asclaimed in claim 6, further comprising: a hydraulic pressure sensor,detecting a pressure of oil on a sucking side of the first oil in thesecond pump, and based on a determination that an oil pressure detectedby the hydraulic pressure sensor has increased to a value substantiallyconsistent with the estimated value of the pressure value of the oilsupplied to the hydraulic operation part, the control that graduallydecreases the target rotation speed of the second pump ends, and thetarget rotation speed of the second pump is decreased until asubstantial stop rotation speed.